4-Phenylbutyrate protects against atherosclerotic lesion growth by increasing the expression of HSP25 in macrophages and in the circulation of Apoe^−/− mice

Endoplasmic reticulum stress plays an important role in cardiovascular disease (CVD) and atherosclerosis. We aimed to assess the ability of 4-phenylbutyrate (4-PBA), a small chemical chaperone administered via drinking water, to reduce atherosclerotic lesion size in chow-fed apolipoprotein (Apo) e^−/− mice and to identify mechanisms that contribute to its antiatherogenic effect. Chow-fed 17-wk-old female Apoe^−/− mice treated with 4-PBA–supplemented drinking water for 5 wk exhibited smaller lesions as well as increased plasma levels of heat shock protein (HSP) 25, the mouse homolog of human HSP27, compared with controls. In addition, 4-PBA inhibited cell death and increased HSP27 expression as measured by real-time PCR and immunoblotting, as well as induced nuclear localization of its transcription factor, heat shock factor 1, in human monocyte/macrophage (THP-1) cells. Furthermore, HSP27 small interfering RNA diminished the protective effect of 4-PBA on THP-1 macrophage attachment and differentiation. In summary, drinking water containing 4-PBA attenuated early lesion growth in Apoe^−/− mice fed a chow diet and increased expression of HSP25 and HSP27 in macrophages and HSP25 in the circulation of Apoe^−/− mice. Given that increased expression of HSP27 is inversely correlated with CVD risk, our findings suggest that 4-PBA protects against the early stages of atherogenesis in part by enhancing HSP27 levels, leading to inhibition of both macrophage cell death and monocyte-macrophage differentiation.—Lynn, E. G., Lhoták, Š., Lebeau, P., Byun, J. H., Chen, J., Platko, K., Shi, C., O'Brien, E. R., Austin, R. C. 4-Phenylbutyrate protects against atherosclerotic lesion growth by increasing the expression of HSP25 in macrophages and in the circulation of Apoe^−/− mice. FASEB J. 33, 8406–8422 (2019). www.fasebj.org.